Empty's Body impl `Error = Infallible` makes `Empty::new()` unable to be used w/ Body constraints

[juliusl]

Empty has generic parameter for Data, so it would be nice to have a generic parameter for Error as well so that Empty::new() can be used w/ functions that set constraints on Body i.e B: Body<Error=..>

[nwtgck]

@juliusl
Does http_body_util::Empty::new().map_err(|_: Infallible| unreachable!()) solve your problem?
To explicitly specifying anyhow::Error, you can use .map_err::<_, anyhow::Error>(|_: Infallible| unreachable!())